Composite aluminum article and aluminum alloys



United States Patent "ice 3,285,717 COMPOSITE ALUMINUM ARTICLE AND ALUMINUM ALLOYS Edward F. Fischer, Cleveland, Ohio, assignor to Aluminum Company of America, Pittsburgh, Pa., :1 corporation of Pennsylvania No Drawing. Filed Aug. 10, 1964, Ser. No. 388,674 11 Claims. (Cl. 29197.5)

This invention relates to aluminum alloys possessing very high wear resistance and hardness at both room and elevated temperatures and to articles of manufacture embodying these alloys.

It is known that aluminum base alloys having a relatively high hardness are better adapted to serve in pistons for internal combustion engines and various other applications requiring wear resistance than the softer alloys. These harder alloys exhibit typical initial Brinell hardness values of up to about 130 at room temperature and residual hardness values often less than half the initial value upon cooling after prolonged exposure to temperatures of 500 F. or 600 F. Also, the Brinell hardness at such temperatures is generally less than 25 after 1000 hours exposure. These limitations on hardness and resistance to wear have restricted the use of these alloys.

Accordingly, it is a principal object of the invention to provide an aluminum alloy possessing greatly improved wear resistance and hardness, both at room temperatures and at elevated temperatures, even after prolonged exposure to elevated temperatures.

Another object of the invention is to provide wear resistant members of the alloy.

Still another object of the invention is to provide an article of manufacture comprising an aluminum or aluminum alloy base member having at least a portion of the surface covered with a much harder alloy that also possesses improved resistance to wear.

Basically, the invention resides in providing an alloy composition consisting essentially of aluminum, 12% to 30% silicon, to 30% copper, 2% to 6% manganese and up to 6% iron, the total of the iron and manganese being at least 3% but not more than 8%, all percentages.

being by weight. A further requirement is that the total amout of the foregoing alloy additions should not be less than 35%, preferably between 40% and 55%, of the total weight of the alloy. Alloys within this composition range exhibit a marked improvement in hardness and wear resistance over prior aluminum base alloys, both at room and elevated temperatures and, further, tend to substantially retain their hardness after prolonged temperature exposure. The alloy is characterized by a Brinell hardness of at least 150 at room temperature before the alloy is exposed to an elevated temperature. Hardness values of up to 281 have been attained and values at 500 F. of from 80 to 180 have been obtained after a 1000 hour exposure. The Brinell hardness values given herein were determined in accordance with the American Society for Testing Materials Standard Methods B-10. Ina preferred embodiment of the invention, the alloying elements are present in amounts of 18% to 22% silicon, 13% to 17% copper, 3% to 5% manganese and up to 2% iron, the total amount of iron and manganese ranging from 4% to 5%, the combined total of :all of these elements being at least 40% of the weight of the alloy. For example, an

3,285,717 Patented Nov. 15, 1966 alloy containing 20% silicon, 15% copper, 4% manganese, and 1% iron is a highly useful alloy within this preferred composition range. Generally, alloys of the preferred composition range exhibit somewhat better weldability and castability than those of the broader composi tion range.

In addition to the elements set forth above, minor additions of 0.5% to 5% nickel, 0.5% to 3% chromium, and 0.5% to 1% of various other metals such as titanium, vanadium, tungsten, molybdenum, etc., may be made without departing from the scope of the invention provided the total amount of these elements does not exceed 5% of the alloy.

If the principal alloying elements are present in amounts less than those set forth above, the alloy will not exhibit the desired improvement in hardnes. In this respect it is particularly noteworthy that a significant improvement in hardness characteristics is realized if the total silicon, copper, manganese and iron content exceeds 40% of the alloy. If the alloying elements are added in amounts greater than those set forth above, the alloy will have a tendency to exhibit excessive hot shortness or an impracticality high melting point, or both, thus limiting its utility.

Generally speaking, the alloy exhibits some tendency tobe hot short but is still castable. However, many useful articles, including long slender items such as weld rods, may be cast without undue dilficulty. For example, rods approximately or inch in diameter may be cast and used in a welding unit for depositing a layer of the alloy on a base material or article. In this respect it is to be noted that the preferred composition offers a particular advantage of a combination of superior castability and weldability. In addition to serving in cast form the alloy can be comminuted and employed in powder form, according to powder metallurgy techniques, to make various articles, especially some that are diflicult to cast. Also, the powder can be used in such processes as plasma arc surfacing.

The aluminum alloy is very hard and highly wear resistant throughout a relatively wide temperature range, as mentioned above, and it is especially well adapted to application to the surface portion of an aluminum or an aluminum base alloy article to form a relatively thin layer or band.

A tabulation of the Brinell hardness values exhibited by various alloys within the ranges set forth above at room temperature, and at 500 and 600 F. for 1000 hour exposure periods are given in Table I. Several commercial.

alloys that have been used for service at elevated temperatures are included for comparison, the alloy being identified by their commercial designations.

As apparent in Table I, my alloys offer a pronounced improvement in hardness over the prior compositions, some of the alloys exhibiting room temperature Brinell hardness values over 230 and as high as 281, and that an improvement is also obtained at both room and elevated temperatures after prolonged exposures at the elevated temperatures. The improved room temperature hardness is substantially retained after relatively severe 1000 hour exposures to 500 F. or 600 F. temperatures. It is further observed that the minimum hardness at 600 F. after a 1000 hour exposure was 45 BHN, and most are over BHN, as contrasted with the conventional alloys which exhibit values of 23 BHN maximum.

TABLE I.B RINELL HARDNESS VALUES (BHN) Residual Room Tempera- Hardness at Elevated Tem- Nominal Composition-Percent Balance Aluminum Initial Room ture Hardness Alter 1,000 perature After 1,000 hrs. Sample or Temperature hr. Exposure to Alloy N 0. Hardness (Prior to Heating) Si Cu Mn Fe 500 F. 600 F. 500 F. 600 F.

20 12 2 1. 168 146 132 86 53 18 2 1. 5 193 176 168 104 69 20 12 4 1. 5 175 169 166 97 78 20 12 2 1. 5 158 138 115 82 45 20 24 2 1. 5 247 222 214 135 100 20 24 4 2 281 238 260 180 125 20 18 4 2. 5 229 207 188 137 93 20 24 6 247 222 224 143 103 20 12 4 2. 5 199 158 145 99 62 28 12 4 2 232 173 158 121 89 20 18 2 2 185 158 150 96 61 20 18 6 1. 5 281 247 260 179 139 20 24 4 2 274 222 247 158 122 16 24 4 2 219 209 204 132 87 12 30 4 2 241 235 235 153 98 .9 Cu, 1.1 Mg, .9 Ni 130 52 48 24 13 .5 Mg, 2 Ni 117 60 44 31 14 011, 1.2 Mg, 2.5 N 105 70 67 37 23 .2 Mg 109 88 66 45 22 Another factor of interest in the utilization of the high hardness alloy is the thermal expansion coefficient, some typical values being those listed in Table II. The sample numbers designated in Table II correspond to those in Table I. Also listed for comparison purposes are values for pure aluminum which approximate those of many commercial alloys.

While, as indicated in Table II, the coefiicient of thermal expansion for the high hardness alloy is less than that of most commercial base alloys, they are compatible therewith. This lower expansion offers some advantage where the alloy is applied about a circumference of a base member since, because of the different rates of expansion, the interface or bond between the base member and the wear resistant surface portion will be in compression. For example, when the alloy is applied as a circumferential band about an automotive piston, the lower thermal expansion of the alloy band will place the band-piston interface in compression thus providing a bond which tightens with increasing temperature. This differential in thermal expansion will not, in most practical applications, cause excessive stresses in the high hardness alloy which, because of its low ductility, might be expected to crack. Several prolonged exposures to temperatures of 600 F. and even approaching 1000 F. have not revealed any such tendency.

As mentioned above, the alloy exhibits extremely good wear resistance, in addition to high hardness, which renders it very useful for many applications. The results of various tests have demonstrated its superior wear resistance. For example, in two 6 cylinder diesel engines, tests were made to determine the wear resistance of the alloy as a facing in piston ring grooves. The high hardness metal was deposited in a large groove and a smaller groove was machined in the weld deposit to receive a conventional piston ring. A cast weld rod was used as the source of the alloy. Each engine included three standard pistons and three with a weld deposited layer of the hard alloy in the compression ring grooves. The body of the piston base alloy was composed of alloy 4032 shown in Table I which has often been used for this pur pose because of its hardness and strength. The specific alloy used for the Weld metal layer nominally consisted of 20% silicon, 15% copper, 4% manganese, 2% iron and balance aluminum. One engine was checked after 119,000 miles of service and the other after 83,000 miles, the period of checking being arbitrary and not based on any failure. The average top ring groove wear is tabulated for both engines in Table III.

TABLE III.AVERAGE TOP RING GROOVE WEAR commercial alloy. Also, it should be noted that, for the standard alloy, the measured wear was roughly proportional to the miles of service but, for the hard alloy, apparently reached a maximum and leveled off after relatively short mileage. As a further note, it was found on examining the pistons that considerable plastic deformation had occurred in the shoulder are-as of the grooves in standard pistons compared to none in the hard surfaced grooves.

Another Wear resistance test which illustrates the outstanding Wear resistance of the alloy was performed on an army tank. The steel tracks on the tank were supported at various points along its continuous length by aluminum idler wheels which often tend to exhibit excessive Wear caused by rubbing against the steel track guides. The test consisted of a 3,300 mile road test comparing two types of wheels, one of a conventional aluminum base alloy nominally composed of aluminum, 0.8% silicon, 4.4% copper, 0.8% manganese, 0.4% magnesium, and the other having the same alloy wheel body, but covered on its wear surfaces with a high hardness alloy having the nominal composition of 20% silicon, 15% to 18% copper, 4% manganese, 2% iron and balance alumi num. The latter alloy was weld deposited as a layer which was subsequently machined to wheels of the required dimensions. A cast weld rod of the alloy was used in a tungsten inert gas shielded are. The average wear for the bare wheels was 0.0005 inch per mile of tank travel; for the hard surfaced wheels wear was reduced to one tenth of this value, 0.00005 inch per mile.

It is to be noted that in both of the above tests, i.e., the piston and tank wheel tests, the high hardness alloy was deposited as a welded layer on the aluminum alloy base by use of standard welding procedures. The deposit was then machined to the desired configuration and finish. Considering its high hardness and high silicon content, the weld deposited alloy possessed relatively good machineability.

While the embodiments described above show the weld deposition of the high hardness alloy on an aluminum alloy base member, this is not a limitation on the invention. A member of the alloy may be affixed or bonded to the base member by a variety of methods, either mechanical or metallurgical, including fusion deposition techniques other than welding, such as metal spraying, and other methods will suggest themselves to those skilled in the art. For example, the preferred alloy composition in powder form has been successfully used in the plasma arc surfacing method. This method offers considerable economic advantage over most other methods and, to this extent, is considered to be one of the preferred methods. Further, reference to an aluminum alloy base member is intended to also include a generally less preferable pure aluminum base. Thus articles comprising an aluminum base alloy (or aluminum) base member and a hard surface member or portion composed of my alloy and bonded to the base member fall within the scope of the invention.

Another advantage afforded by the high hardness alloy over various conventional alloys is that it may be used in the as-machined condition without any chemical, heat or other treatment to improve its surface hardness. A still further significant advantage is that members covered in whole or in part with the alloy may be subjected to various heat treatments, such as artificial aging or annealing, and still retain a high residual hardness level. Coated base members have been subjected to solution heat treatments at temperatures of over 900 F. without seriously affecting the hardness of the high hardness surface layer.

In addition to being used on members as initially fabricated, the high hardness alloy is well adapted to reconditioning applications; for example, worn pistons have been successfully reconditioned by weld depositing the alloy in the worn ring groove area and rem-achining the groove.

It is to be understood that the above description is intended to be illustrative of and not in limitation of the invention or its applications. Those skilled in the art will find many uses for this exceptional alloy.

What is claimed is: Y

1. An aluminum alloy consisting essentially of aluminum, 12% to 30% silicon, to 30% copper, 2% to 6% manganese, up to 6% iron, the total amount of said iron and manganese being 3% to 8% and the combined total amount of said silicon, copper, manganese and iron being at least 35 the said aluminum alloy beng characterized by high resistance to wear at room and elevated temperatures and an initial room temperature Brinell hardness of at least 160.

2. An aluminum base alloy according to claim 1 Wherein the total amount of said silicon, copper, manganese and iron is between 40% and 55%.

3. An aluminum alloy consisting essentially of aluminum, 18% to 22% silicon, 13% to 17% copper, 3% to 5% manganese, up to 2% iron, the total amount of said iron and manganese being 4% to 5%, the combined total of said silicon, copper, manganese and iron being at least 40%, the said aluminum alloy being characterized by high resistance to wear at room and elevated temperatures and an initial room temperature Brinell hardness of at least 150.

4. An article having high resistance to wear and a minimum Brinell hardness at room temperature of 150 composed of an aluminum alloy consisting essentially of aluminum, 12% to 30% silicon, 10% to 30% copper, 2%

' to 6% manganese, up to 6% iron, the total amount of said iron and manganese being 3% to 8%, and the combined total of said silicon, copper, manganese and iron being at least 35%.

5. An article according to claim 4 wherein the total of said silicon, copper, manganese and iron is between 40% to 55 6. An article having high resistance to Wear and a minimum Brinell hardness at room temperature of 150 composed of an aluminum alloy consisting essentially of aluminum, 18% to 22% silicon, 13% to 17% copper, 3% to 5% manganese, up to 2% iron, the total amount of said iron and manganese being 4% to 5%, the combined total of said silicon, copper, manganese and iron being at least 40%.

7. A composite article comprising a base member of an aluminum base alloy and a hard face member affixed to said base member, said hard face member being composed of an alloy consisting essentially of aluminum, 12% to 30% silicon, 10% to 30% copper, 2% to 6% manganese, up to 6% iron, the total amount of said iron and manganese being 3% to 8%, the combined total of said silicon, copper, manganese and iron being at least 35%, said hard face member being characterized by high resistance to wear at room and elevated temperatures and by an initial room temperature Brinell hardness of at least 150.

8. A composite article according to claim 7 where the total amount of all alloying components, except aluminum, is between 40% and 55 9. A composite article according to claim 7 wherein the said hard face member is fusion deposited on the base member.

10. A composite article as in claim 7 wherein the said hard face member is applied to the base member by plasma arc surfacing.

11. A composite article comprising a base member-of an aluminum base alloy and a hard face member affixed to said base member, said hard face member being composed of an alloy consisting essentially of aluminum, 18% to 22% silicon, 13% to 1 7% copper, 3% to 5% manganese, up to 2% iron, thetotal amount of said iron and manganese being 4% to 5%, the combined total of said silicon, copper, manganese and iron being at least 40%, said hard face member being characterized by high resistance to wear at room and elevated temperatures and by an initial room temperature Brinell hardness of at least 150.

References Cited by the Examiner UNITED STATES PATENTS 1,829,668 10/1931 Morrill I43 2,044,294 6/1936 Handler. 2,956,846 10/1960 McCullough.

HYLAND BIZOT, Primary Examiner.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,285,717 November 15, 1966 Edward F. Fischer It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 2, line 52, for "alloy" read alloys column 3, TABLE II, fourth column, line 3 thereof, for "14." read Signed and sealed this 19th day of September 1967.

(SEAL) Attest:

ERNEST W. SWIDER Attesting Officer EDWARD J. BRENNER Commissioner of Patents 

1. AN ALUMINUM ALLOY CONSISTING ESSENTIALLY OF ALUMINUM, 12% TO 30% SILICON, 10% TO 30% COPPER, 2% TO 6% MANGANESE, UP TO 6% IRON THE TOTAL AMOUNT OF SAID IRON AND MANGANESE BEING 3% TO 8% AND THE COMBINED TOTAL AMOUNT OF SILICON, COPPER, MANGANESE AND IRON BEING AT LEAST 35%, THE SAID ALUMINUM ALLOY BEING CHARACTERIZED BY HIGH RESISTANCE TO WEAR AT ROOM AND ELEVATED TEMPERATURES AND AN INITIAL ROOM TEMPERATURE BRINELL HARDNESS OF AT LEAST
 150. 